This application claims the priority of German Patent Document DE 199 50 504.7, filed Oct. 20 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a process and apparatus for the control of the light distribution of a headlight arrangement of a vehicle. Preferred embodiments relate to such process and apparatus which includes at least one first light sensor which senses light emissions acting on a driver of the vehicle from an area (I) of the opposite side of the road, a comparator device which compares the intensity of the light emissions in each area with a threshold value, a control device for the light distribution of the headlight arrangement as a function of a signal of the comparator device, where the control device, on overshoot of the threshold value in an area (I) sensing the opposite side of the road, sets the light distribution so that the illumination of an edge of the road of the driver""s own side of the road is increased wherein the light distribution in the sense of an increase of the illumination of the edge of the road of the driver""s own side of the road a turn-off delay is provided.
In the case of a generic process for the control of the light distribution of a headlight arrangement according to German Patent Document DE 38 44 364 C2, the driver""s own side of the road is illuminated at an increased light level to avoid a reduction of the ability of the driver of a vehicle to see when oncoming traffic is present. For this purpose a light sensor registers various areas of a visual field of the driver and the light level for the illumination the driver""s own side of the road is increased if a threshold value for the light emissions from the area of the opposite side of the road is exceeded. If, however, a threshold value for the light emissions from the area of the driver""s own side of the road is exceeded or a threshold value for the light emissions for an area above the road is exceeded, then the light level is reduced once again. For the increase of the light level, an additional headlight is provided for dimmed light, said additional headlight being switched on in the previously described manner. Alternatively a movable shutter is provided in a headlight already present with which the light distribution can be changed. Instead of the movable shutter the light source can also be shifted, so that the position of the point of highest light intensity shifts.
With respect to this state of the art it is an objective of the invention to provide an improved process and an improved apparatus for the control of the light distribution of a headlight arrangement of a vehicle.
According to the invention this objective is realized by providing a turn-off delay for the light distribution in the sense of an increase of the illumination of the edge of the road of the driver""s own side of the road. By this measure the light intensity in the area of the driver""s own side of the road is not increased discontinuously but rather gradually. Thereby it is avoided in an advantageous manner that for the driver, whose eyes during the increased illumination had become accustomed to the greater amount of light, a dark space arises after the passing of the oncoming traffic by a sudden withdrawal to the increased illumination in the area of the driver""s own side. In addition the number of the switching processes recognizable for the driver is reduced in the case of moderately dense oncoming traffic.
Advantageous extensions of the invention are described below and in the claims.
Thus it is proposed to perform the turn-off delay with a delay of approximately 2 to 10 seconds. This measure is based on the recognition that this time is sufficient so that the eye of the driver can accustom itself to the reduction of illumination. If, in this case, the upper limit is chosen, then the reduction of the illumination for the driver is hardly still perceptible. An additional increase of the delay time then leads to no additional improvement of the adaptation.
Furthermore, it is proposed in addition to the turn-off delay to provide also a turn-on delay. This should then preferably have a delay time of at most 2 seconds. By this measure the turn-on of the additional light acts less irritatingly on the driver. On the other hand it must be noted that a noticeable turn-on is desirable in order to divert the gaze of the driver to the right edge of the road.
Before the turn-off delay a deadtime of up to 3 seconds can be provided in addition in order to compensate for that time span which lies between the point in time at which the oncoming vehicle leaves the sensing area of the light sensor and the point in time at which the oncoming vehicle leaves the area visible to the driver.
For this purpose a light sensor senses various areas of a field of vision of the driver and the light level for the illumination of the driver""s own side of the road is increased if a threshold value for the light emissions from the area of the oncoming traffic is exceeded.
Furthermore, it is advantageous if the threshold value for the light emissions from the area of the opposite side of the road at which the illumination of the edge of the road is increased, is determined as a function of ambient brightness. In this case the threshold value should increase with increasing ambient brightness so that the increase of the illumination of the edge of the road is only done when the light emissions from the area of the opposite side of the road lie by a certain amount or percentage above the ambient brightness in order thus to avoid an unnecessary increase of the illumination of the edge of the road.
Also it can be provided to perform the increase of the illumination of the edge of the road only within a predetermined range of speed. The lower limit of this range should be chosen so that it is characteristic for city traffic. In Germany this value can lie around 30 km/h. Thereby it is prevented that within the area of the city (usually illuminated anyway) with partially heavier oncoming traffic, in stop-and-go traffic, in standing traffic (for example, before a stop light) or in congestion by blinking lights, taillights, or reflections a frequent or even continuous additional illumination is triggered in the vehicle traveling forward.
The upper limit of this range should on the contrary be chosen so that it is characteristic for freeway travel. In Germany this value could lie at around 120 km/h. Thereby the illumination of the edge of the road will not be increased unnecessarily on the freeway, on which there can be no oncoming traffic in the direct sense. The limited range would offer moreover no real help at higher speeds.
According to advantageous features of preferred embodiments of the process, it is further proposed to turn headlights on or off for the setting of a light distribution. This setting of the light distribution distinguishes itself by a particularly simple setup and lower control expenditure. In particular it is proposed to provided a dimmed light known in itself for the illumination of the driver""s own side of the road and an additional headlight for the illumination of the edge of the road.
Finally, it is proposed according to the apparatus to dispose the light exit area of the additional headlight in the light exit area of a headlight already present. By this measure in an advantageous manner on turning on of the additional headlight no new surface to be illuminated is provided which could distract or even irritate the oncoming driver. For such a common light exit for example, the additional headlight can be disposed in the area of the dimmed light or can be combined with a parking light.
For this purpose a dimmed light and an additional headlight or parking light could, for example, be disposed in a common reflector. It is also contemplated to dispose the additional headlight and the dimmed light under a common cover plate and to illuminate in addition the space formed around the two headlights with the aid of an additional source of illumination, such as, for example, the parking light, so that despite the separate light generation systems the goal of a single headlight is maintained.